3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), an evolution of UMTS (Universal Mobile Telecommunications System), is introduced as 3GPP release 8. 3GPP LTE adopts Orthogonal Frequency Division Multiple Access (OFDMA) for downlink and Single Carrier-Frequency Division Multiple Access (SC-FDMA) for uplink. Multiple Input Multiple Output (MIMO) is employed of having up to four antennas. Recently, an advanced version of 3GPP LTE, 3GPP LTE-advanced (LTE-A), is actively on discussion.
User equipment (UE), while being serviced from a specific cell, may be interfered by radio signals transmitted from another cell. User equipment periodically measures cells and reports a measurement result. In case user equipment performs handover to another cell, it may perform measurement on a neighboring cell as well as a serving cell and may report a result. In measuring the specific cell, interference caused by radio signals from other cells renders it difficult for the user equipment to normally measure the specific cell. This deteriorates mobility of the user equipment in the wireless communication system.
In particular, under the situation where macro cells, pico cells, and femto cells are co-existent, for example, when different service coverage, different frequency channel bands, and different RATs (Radio Access Technologies) serviced by cells, schemes for avoiding interference caused by the cells may be considered more critical.
Inter-cell Interference Coordination (ICIC) is a task that operates radio resources so as to maintain control of inter-cell interference. The ICIC mechanism may be divided into a frequency domain ICIC and a time domain ICIC. The ICIC includes multi-cell Radio Resource Management (RRM) functions that require consideration of information from multi-cells.
The frequency domain ICIC coordinates use of frequency domain resources (e.g., Resource Block (RB)) between multi-cells. The time domain ICIC coordinates time domain resources (e.g., subframe) between multi-cells.
In the ICIC, depending on targets for which the user equipment performs measurement, targets causing interference (i.e., interfering cell) and targets damaged by interference (i.e., interfered cell) are determined.
If user equipment approaches the coverage of a neighboring cell that cannot be accessed, the user equipment may be highly interfered. To prevent the situation where UEs inaccessible to the neighboring cell cannot perform communication due to interference caused by the neighboring cell, the neighboring cell may transmit and receive wireless signal transmission signals with measurement resources limited.
Meanwhile, in a communication environment with severe interference, a network may have a difficulty in transferring an optimal measurement configuration to the user equipment. The user equipment may apply a common measurement configuration in a normal environment and may apply another measurement configuration proper for an environment with severe interference in such severely interfered environment. However, whenever high interference occurs, receiving a report from the user equipment and transmitting another measurement configuration may cause signaling overhead. To address such problem, there is a need for a method of being able to sense a situation where the user equipment is going to vary the measurement configuration and accordingly may apply the varied measurement configuration on its own.